Friday, July 4, 2008
What is a bowel obstruction?
Small bowel obstructions are ubiquitious in the world of general surgery. Most surgeons have one or two lingering on their in-house list at any one time. In the above post, I discussed an unusual cause of SBO, but over 90% are secondary to adhesions. What are adhesions? Scar tissue, baby. Anytime a surgeon has had his/her grubby hands inside your belly, it incites an inflammatory reaction that leads to the formation of fibrous bands and webs. The adhesions can form anywhere; bowel to bowel, bowel to liver, bowel to abdominal wall, just about anything. Generally, the scarring isn't a problem but you have to realize the intestines are constantly in motion, peristalsing and wiggling around inside your belly. Every once in a while, a segment of bowel will flop around a band of scar tissue and it will twist in such a way that the lumen gets either partially or completely occluded.
What does an SBO feel like?
Crampy abdominal pain. Your belly swells. You can't move your stool. You get more and more nauseated until you start vomiting bile in torrents of green. It's miserable, in a word.
What can I do to avoid one?
Nothing. It's not your fault, there's no dietary changes you can implement, no exercise regimen, nothing. A history of abdominal surgery gives you about a 10-20% risk of developing a significant bowel obstruction. Sometimes I use an adhesion barrier product called "Seprafilm" at the end of an open case in the hope that future adhesions will be reduced. There isn't a lot of science to suggest Seprafilm and its competitors actually work, but theoretically it's worth a try. For what it's worth.
What's the treatment?
Most cases can be managed non-operatively. In fact, 70-75% of cases of SBO can be managed without the knife. The key tenets of management are bowel rest, nasogastric decompression, and aggressive rehydration. As a result of vomiting and third spacing of fluid in the bowel wall, patients can get quite dehydrated. You're going to need a couple of liters of saline pumped into you upon arrival in the hospital. And then you're going to have to endure the placement of the dreaded NG tube. On the list of top ten most painful things to undergo, getting an NG tube ranks just below "sawing off your own arm with a penknife to escape from underneath the giant boulder that has you trapped in the desert." Actually it's not that bad. Most of the time it goes in nice and smooth. Just lean forward, sip some water, and try not to fight it too much. The tube is very important and it needs to go down. It's a hose you drop into an overflowing toilet. The sump pump in your flooded basement. Usually a liter or two of foul, feculent greenish-brown slop gets sucked up immediately with a high grade obstruction.
When do you decide to operate Mr. Buckeye Surgeon?
Rarely is it necessary to zip someone off to OR the minute you see them in the emergency room. Bowel obstructions from incarcerated hernias and colonic obstructions obviously need immediate attention. But most SBO's can intially be managed non-operatively. The old adage "never let the sun set on a bowel obstruction" is a little dated. Sort of like catgut sutures and surgical residents working more than 80 hours in a week.
I monitor three things:
1. Pain: Increasing pain suggests bowel ischemia. This is the number one factor I pay attention to. Pain that develops despite NG decompression mandates a trip to the OR. Patients who present with pain will sometimes feel better after a couple hours of NG suctioning. The key thing is to examine the patient serially.
2. White blood cell counts: WBC counts ought to decrease over the first 24-48 hours. Persistent or rising counts are worrisome.
3. Xrays: Least reliable. If the NG is doing its job, the films may very well look better the following day. That doesn't mean the obstruction has resolved, though; it simply means the proximal bowel has been adequately decompressed. Persistent stacked loops of bowel, however, imply a possible closed loop obstruction (proximal and distal ends of a segment of bowel blocked), which will not get better without an operation.I also like CT scans for SBO's. It's a great tool for predicting the likelihood of spontaneous resolution of a patient's bowel obstruction. I look for transition points and possible occult hernias not appreciated on physical exam.
Ultimately, there is no magic formula. It's a judgment call. If the patient isn't progressing, then an operation is justified. The operation itself can often be one of the quickest abdominal procedures in all of general surgery. Sometimes it's a matter of one snip of a single band that has kinked the bowel. Other times, it can be one of the more stressful, time-consuming, and hazardous procedures one will encounter. Patients with multiple previous operations or those who have had radiation treatments for a previous cancer will develop what is known as a "frozen abdomen". Everything is matted together in a single mass. The fused loops of bowel almost look like the surface of a brain. Hours are spent just getting into the abdomen. It's an operation that demands patience and some cool tunes in the background. You can't rush. It shouldn't be a case you do at the end of a long day. Nor should it be the first case on a day when you have five others scheduled. I use the scalpel, for the most part. There's no role for electrocautery; not unless you want to take care of the patient's entercutaneous fistula in a few weeks. It's all sharp dissection, tediously slicing and shaving your way to something at least resembling normal anatomy. It's like carving a serpent out of cement. You can't go on autopilot, like for an inguinal hernia or an elective gallbladder. Every move is an act of improvisation....It's actually sort of fun.